When I think about it, I don't see why blockland wouldn't be rated E. Seeing as offline is the only thing they would rate by default there's not much? Mild/fantasy violence? Other than that there's no blood, there's no language (literally it's just "ow" and "aah"). Addons don't count because they're online interactions. Even like the pirate DM would be E.
Also I dig that cover, filipe. Only thing I could really see it using is default blockhead as the main character and make him on a horse for the ladies.